Thermal conductivity measurements at room temperature are presented as the basis for certified values of Standard Reference Material 1453, Expanded Polystyrene Board. The measurements have been conducted in accordance with a randomized full factorial experimental design of two variables, bulk density and temperature, using the National Institute of Standards and Technology one-meter line-heat-source guarded hot plate. Uncertainties of the measurements, consistent with current international guidelines, have been prepared. The thermal conductivity measurements were conducted over a range of bulk density of 37.4 to 45.8 kg/m3 and mean temperature of 281 to 313 K. Statistical analyses of the physical properties of Standard Reference Material 1453 are presented and include variations between boards, as well as within board.